Principal component analysis of the t-wave for mortality Prediction in hemodialysis patients.

PRINCIPAL COMPONENT ANALYSIS OF THE T-WAVE FOR MORTALITY PREDICTION IN HEMODIALYSIS PATIENTS Patients undergoing hemodialysis (HD) therapy often experience alterations in cardiac excitability and have accounting for an estimated 3-year cumulative probability of cardiovascular death of 39.5% of total deaths [1]. Abnormalities in ventricular repolarization and its dispersion could be a cause of HD-induced arrhythmogenic effect. Nowadays, no ECG-derived parameter has been proven to predict the risk of cardiovascular death. QT dispersion (QTd) has been proposed, however, some concerns have been raised about uncertainty of the QT dispersion measurement and technical difficulties in measuring the QT interval. Principal component analysis (PCA) of the T-wave vector applied to 12-lead recordings has been proposed to obtain an ECG marker of vulnerability to ventricular arrhythmias and of cardiovascular mortality [2]. Several studies showed that the ratio of the second to first eigenvalues (PCA ratio) more accurately represents repolarization abnormalities than QTd in a large general population sample [3,4]. The aim of this study was to explore the predictive value of the PCA ratio parameter for all-cause and cardiac mortality in a retrospective study on HD patients. METHODS The selected subjects were 122 patients (46 women and 76 men, mean age 77\ub110) in whom digital ECG recordings were available for the analysis from previous clinical studies. Standard holter 12-lead recordings (H-12 Holter, Mortara Instrument Inc., Milwaukee, Wisconsin, USA) were collected starting with the dialysis session. ECGs were sampled at 180 Hz or 1kHz and stored to a PC hard disk for subsequent analysis. PCA is an established method for representing data and, when applied to T-wave, it describes features of repolarization in a manner that is less dependent on precise determination of T-wave offset. Singular value decomposition was applied to the covariance matrix of the raw ECG data corresponding to T-wave from the eight independent ECG leads. Then, the main eigenvectors of the spatial T-wave were computed. The first eigenvector accounts for most of the energy in repolarization when applied to the normal T-wave vector, whereas inhomogeneous repolarization, if present, is indicated by a relevant contribution of the second and third components. Thus, the ratio of the second to first eigenvalues of the spatial T-wave vector (PCA ratio) generated from the 12-lead digital ECG serves as a measure of T-wave complexity or heterogeneity of repolarization, with increasing values referring to higher amount of complexity. As shown in fig. 1 the PCA ratio provides information that can be visualized by analogy as the long and short axes of the three-dimensional T-wave loop and provides an estimate of the relative fatness of the T-wave loop relative to its peak amplitude, in which a fatter loop with a higher PCA ratio reflects more complex Twave morphology. A median value of PCA was computed for each patient throughout the whole ECG recording. Following the Strong Heart Study [3] a threshold for PCA ratio in men and women, independently of gender, was defined as 28%. Deaths were identified in an ongoing surveillance in each dialysis center and were verified through review of medical records. Deaths were classified as cardiac if caused by myocardial infarction, sudden death from CHD, or congestive heart failure by an independent review panel of physicians unaware of PCA ratio findings. After a maximum follow-up of 5 years, patients were censored as dead or alive considering the days from the date of the first ECG recording. Patients were then divided in two groups depending on the median PCA ratio value. Endpoints were all-cause mortality and cardiac mortality. Mortality rates were calculated and plotted according to the Kaplan-Meier analysis. P<0.05 was considered significant. RESULTS AND DISCUSSION During the fo..

Calcium profiling in hemodiafiltration: a new way to reduce the calcium overload risk without compromising cardiovascular stability.

Low and high dialysate calcium (Ca\ub2\u207a) content may have positive and harmful effects depending on the considered pathological aspect: hemodynamic instability, cardiac arrhythmias, parathormone release, adynamic bone disease, cardio-vascular calcifications. We hypothesized that a time-profiled Ca\ub2\u207a concentration would keep the cardiovascular advantages of high Ca\ub2\u207a but would reduce the risk of calcium overload.A prospective, multicenter study using a particular hemodiafiltration technique that allows the profiling of electrolytes was designed. Patients (n = 22) underwent randomly a 3-week dialysis session with low and high constant dialysate Ca\ub2\u207a (Ld(Ca,), 1.25 mM and Hd(Ca,), 2 mM) and profiled Ca\ub2\u207a (Pd(Ca)), respectively. Plasma and spent dialysate Ca\ub2\u207a, systolic and diastolic arterial pressure (SAP, DAP) and QT interval corrected for heart rate (QTc) were analyzed.Plasma Ca\ub2\u207a concentration decreased in Ld(Ca), whereas it increased in Hd(Ca) and to a lesser extent, in Pd(Ca). Total amount of Ca\ub2\u207a given to the patient in Pd(Ca) (15.5 \ub1 1.0 mmol) was higher than in Ld(Ca) (4.3 \ub1 1.6 mmol) but lower than in Hd(Ca) (21.9 \ub1 3.3 mmol). SAP and DAP decreased in Ld(Ca), whereas it was almost constant in both Hd(Ca) and Pd(Ca\ub7). QTc significantly increased, up to critical values (>460 msec), only during Ld(Ca\ub7).Pd(Ca) seems to retain the advantages of high Ca\ub2\u207a in terms of hemodynamic stability and modification of QTc while reducing the excessive positive calcium balance typical of dialysis with high Ca\ub2\u207a content

Influence of plasma potassium changes on the myocardial cell repolarization during hemodialysis

Dialysis therapy has a strong impact on cardiac excitability and the frequency of ectopic beats increases in the course of the session. Dispersion of ventricular repolarization could be a cause of the dialysis arrhythmogenic effect. In fact, QT dispersion increases during dialysis and this increase seems to be related to electrolyte, particularly potassium and calcium, concentration changes. However, some concerns have been raised about uncertainty of the QT dispersion measurement. Principal component analysis of the T wave applied to 12-lead ECG recording has been proposed as a novel approach to study the complexity of repolarization without having to determine the end of T-wave. The aim of this study was to assess and quantify the 24-hour changes in the complexity of ventricular repolarization in patients undergoing hemodialysis by means of principal components analysis. The effects of two dialysis protocols leading to different plasma potassium levels were also analyzed. Twelve patients were studied during Acetate Free Biofiltration with K+ profiling (AFBK). AFBK sessions were classified as Klow and Khigh on the basis of the dialyzate K+ concentration set at the start of the treatment. For each patient four sessions (2 Klow and 2 Khigh) were analysed. Holter 24-hour recordings were collected starting with the dialysis session. Principal components analysis was applied to the T wave automatically extracted from each beat and the repolarization complexity was quantified by the ratio of the second to the first eigenvalue (PCA ratio). Hemodialysis caused a significant increase in the PCA ratio (+50% at the end of the sessions). The PCA ratio recovered to the basal value during the first hour post-dialysis and kept stable during the subsequent 19 hours. When comparing Klow and Khigh sessions the PCA ratio increase was similar during the first two hours of dialysis but it was significantly higher in Klow sessions in the last two hours of dialysis, then the PCA ratio recovered to the same basal value. A difference in the occurrence of ventricular ectopic beats was also pointed out, being the number of premature ventricular contractions (PVCs) significantly higher in Klow sessions in the last three hours of treatment (p<0.05). Results show that hemodialysis significantly increases the T wave complexity. Such an increase is related to the therapy-induced potassium depletion, with greater complexity when lower potassium levels are reached. Moreover, it can be hypothesized that repolarization dispersion changes underlie the observed increase in PVCs occurrence

Divert to ULTRA: Differences in infused volumes and clearance in two on-line hemodiafiltration treatments

Background: Mixed diffusive-convective dialysis therapies offer greater removal capabilities than conventional dialysis. The aim of this study was to compare two different on-line, post-dilution hemodiafiltration (HDF) treatments with regard to achieved convective volume and middle-molecule dialysis efficiency: standard volume control (sOL-HDF) and automated control of the transmembrane pressure (TMP) (UC-HDF). Methods: We enrolled 30 ESRD patients (55.9 +/- 14.0 years, 20/10 M/F) in a randomized, prospective, crossover study The patients received a 3-month period of sOL-HDF followed by UC-HDF for a further 3 months, or vice versa, using the same dialysis machine. In sOL-HDF, fixed exchange volumes were set according to a filtration fraction greater than or equal to 25%. In UC-HDF therapy, the exchanged volume was driven by a biofeedback system controlling the TMP and its set point in a double loop. Patients maintained their treatment time, dialyzer, blood flow rate, and anticoagulant regimen unchanged throughout the study. Results: Greater convective volumes were achieved in UC-HDF than in sOL-HDF (23.8 +/- 3.9 vs. 19.8 +/- 4.8 L; p<0.001) with high pre-dialysis Ht value (sOL-HDF 34.0 +/- 4.5% and UC-HDF 34.0 +/- 4.4%; p = 0.91). The average clearance values of)beta 2m and P were higher in UC-HDF than in sOL-HDF (respectively 123 24 vs. 111 +/- 22 ml/min, p<0.002 and 158 +/- 26 vs. 152 +/- 25 ml/min, p<0.05). Moreover, the UC-HDF mode led to a significantly increased rate of call-free sessions from 88% to 97% (p<0.0001). Conclusions: This study showed that the biofeedback module, applied to the automatic control of TMP in on-line HDF, results in higher convective volumes and correspondingly higher beta 2m and P clearances. By making the HDF treatment more automated and less complex to perform, it significantly reduced the staff workload